脂多糖预处理对大鼠急性胰腺炎IRAK-4表达的影响

Effects of lipopolysacharide pretreatment on the expressions of IRAK-4 in acute pancreatitis rats

目的:观察脂多糖(Lipopolysaccharide,LPS)预处理后白细胞介素-1受体相关激酶-4(Interleukin-1 receptor-associated kinase 4,IRAK 4)表达在大鼠急性胰腺炎(Acute pancreatitis,AP)早期的变化,探讨LPS预处理减轻AP的可能机制。方法:雄性SD大鼠63只,随机分为3组:假手术组(Sham组)、急性胰腺炎(AP组)和LPS预处理组(LPS组),LPS组经腹腔注射LPS,其余两组均给予等体积生理盐水。Sham组造模后3 h取材,其余两组分别于造模后3、6、12、24 h取材。HE染色显微镜下观察各组病理改变,Western blot及RT-PCR法测定胰腺组织IRAK 4蛋白和mRNA表达,免疫组化法检测胰腺组织NF-κB表达,ELISA法检测血浆中TNF-α含量。结果:病理损伤AP组>LPS组>Sham组。AP组IRAK 4 mRNA及蛋白的表达于12 h达到高峰,随后降低,而LPS预处理后其表达明显低于AP组(P<0.01),且随时间的延长无明显改变(P>0.05)。LPS组各时间点NF-κB及血液TNF-α表达明显低于AP组(P<0.01),两组均于12 h达到高峰(P<0.01)。结论:抑制IRAK 4表达,进而抑制NF-κB及TNF-α等的表达,可能是脂多糖预处理对AP保护作用的重要机制之一。

Objective：To discuss the possible mechanism of lipopolysaccharide（LPS） pretreatment in alleviating acute pancreatitis（AP） in rats by detecting the changes in expressions of interleukin-1 receptor associated kinase 4（IRAK-4） in the pancreas.Methods： Sixty three male Sprague-Dawley rats were divided randomly into three groups：sham group,acute pancreatitis group（AP group） and LPS pretreatment group（LPS group）.LPS was injected intraperitoneally to the rats in LPS group while equal amount of normal saline was injected to the rats in the other two groups.Samples were achieved at 3 h after the model was built in sham group while at 3,6,12 h and 24 h after modeling in the other two groups.The morphology of pancreatic tissue was analyzed by light microscopy respectively.The expressions of IRAK-4 gene and protein level of pancreas were determined by reverse RT-PCR and western blot,the activities of NF-κB were detected by immunohistochemical method and the serum TNF-α level was estimated by ELISA.Results： The pathological damage was most serious in AP group,followed by LPS group and sham group.The expressions of IRAK-4 mRNA and protein in AP group reached the peak at 12 h then decreased.The expressions of IRAK-4 mRNA and protein were obviously lower in LPS group and were maintained a lower level（P0.05） compared with those in AP group after the pretreatment（P0.01）.The activities of NF-κB and the level of serum TNF-α were obviously lower in LPS group compared with those in AP group at all time periods（P0.01）,both group reaching the peak simultaneously at 12 h（P0.01）.Conclusion： Down-regulating the expression of IRAK4,NF-κB and TNF-α may be one of the protective mechanisms of LPS pretreatment for AP.